Like most English winemakers, the majority of his exports are of sparkling wines, which account for just over half of the firm's production.

But he points out that exports are only a "part of the story" and the firm is still largely focused on the UK, one of the world's biggest wine markets.

"In the rest of the world there is potential but you need a dose of realism," he says. "It took the French 350 years to export 50% of their champagne and the UK is their largest market."

Producers tend to see certain international markets as better bets than others, preferring places that like wine but don't have huge domestic industries of their own.

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Bob Lindo co-founded Camel Valley in Cornwall

France, Italy and Spain are "hard work", says Bob Lindo, who founded the Cornish winery Camel Valley with his wife Annie in 1989.

But countries such as Japan, China and the US, which is his biggest market, buy much more.

"We are sold in 23 US states now," Mr Lindo says. "There are a lot of parts of America that don't grow wine and there's a very enthusiastic wine culture."

Image copyrightCamel Valley Wines 2017Image caption
The Camel Valley winery in Cornwall has done well in international competitions

Helpfully, English wine has shed its once negative reputation and is doing well in major competitions such as the Euposia International Challenge (Bollicine del Mondo) in Italy, which attracts sparkling wines from around the world.

Organiser Carlo Rossi says English brands regularly make the top 10 in various categories, with wine producers Nyetimber, Hambledon and Camel Valley all having won golds in the recent past.

"About 10 years ago it seemed a joke that the English could make excellent sparkling wine, but there has been a surge in interest," he says.

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Chapel Down grows a variety of grapes at its vineyards, including Chardonnay, Pinot Blanc and Bacchus

Chapel Down's Mr Thompson believes better marketing is the key to exposing the talent in the industry.

He notes how countries such as France play on the fact they are associated with producing fantastic food and drink, "so we buy French, even their lager which isn't actually that good".

"So England needs to sell itself as a quality producer of food and drink, which it still doesn't do well enough and wine can be a flag-bearer."

Not everyone is convinced about English wine, though.

Malcolm Gluck, a British wine critic who has penned numerous books, says there is a "marvellous conspiracy" among winemakers and writers to pretend English wine is great.

"There are English wines that are interesting that cost £12-15," he adds. "But they cost two to three times more than comparable wines from South America or France, Italy and Spain."

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The UK has a shortage of land suited to wine growing

There are other barriers to building a world-beating wine industry, including a shortage of land suitable for grape growing and high set-up costs.

The English climate also limits production mainly to the south of England, although rather perversely, things could improve in that respect because of global warming.

A study last year by climatologists at UCL suggested rising temperatures and rainfall could let vineyards thrive as far north as Elgin near Inverness by 2100.

They also claimed the Thames estuary would become warm enough to grow Malbec grapes.

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Chapel Down's winery in Kent

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Camel Valley's Mr Lindo believes exports will increase gradually as the reputation of English wine flourishes but he's not chasing them. He says he is busy enough catering to restaurants and supermarkets up and down the UK.

He also thinks we should not judge the industry's success by its scale.

"A lot of City money is going into English wine and there is a risk it will become too commercialised," he says.

"You have to be really committed to run a vineyard, but if the market gets flooded, producers who have been here from the start will suffer.

"There's also been a lot of cooperation between English producers and I don't want it to stop."